High levels of vitamin D during pregnancy may lower the risk of wheezing and asthma in offspring during early childhood, according to research presented at the annual meeting of the American Academy of Allergy, Asthma and Immunology in Miami Beach, Florida.

During a press briefing, Dr. Carlos Camargo Jr., of Harvard Medical School in Boston noted that vitamin D deficiency and asthma are both common in the northeastern part of the United States, suggesting that the two may be related. Moreover, while vitamin D has important effects on the immune system, its affect on asthma is not known.

Camargo’s team tracked 1,306 mother-child pairs for more than three years, and used a food frequency questionnaire to assess levels of maternal vitamin D during pregnancy.

By age two, there was a clear association between increasing prenatal levels of vitamin D in the mother and decreasing risk of wheezing or doctor-diagnosed asthma in the child, Camargo said.

The average total vitamin D intake during pregnancy was 550 international units (IU) per day. In a more thorough analysis, a 100-IU increase in maternal vitamin D intake was associated with an odds ratio of 0.90 for “any wheeze” in the child - defined as mother-reported wheeze during the first two years of life.

When the data were adjusted to account for dietary levels of fruit, vegetables, and fish, the results did not change, the authors note in meeting materials. “This inverse association was present for vitamin D from either diet or nutritional supplements.”

Camargo also reported that a preliminary look at the three-year data show a similar strong association between higher maternal vitamin D levels and lower risk of wheezing and asthma at age three years. Continued follow-up is needed to see if the lower risk of wheezing continues as the children grow older, Camargo said.